From 70f2a5d8da82c9331b308b98465b96c3399490d3 Mon Sep 17 00:00:00 2001
From: Peter Tillemans <pti@snamellit.com>
Date: Mon, 2 Dec 2024 08:53:49 +0100
Subject: [PATCH] solved day2

---
 src/2024/day02.lisp        | 61 ++++++++++++++++++++++++++++++++++++++
 tests/2024/day02-test.lisp | 41 +++++++++++++++++++++++++
 2 files changed, 102 insertions(+)
 create mode 100644 src/2024/day02.lisp
 create mode 100644 tests/2024/day02-test.lisp

diff --git a/src/2024/day02.lisp b/src/2024/day02.lisp
new file mode 100644
index 0000000..d622965
--- /dev/null
+++ b/src/2024/day02.lisp
@@ -0,0 +1,61 @@
+
+(defpackage :aoc/2024/02
+  (:use :cl :aoc :alexandria)
+  (:export
+   #:sample-data
+   #:part1
+   #:part2
+   #:deltas
+   #:safe-levels
+   #:safe-levels-with-dampener
+   ))
+
+(in-package :aoc/2024/02)
+
+
+(defun parse-line (s)
+  (map 'list #'parse-integer (cl-ppcre:split " " s)))
+
+(defvar input-data '())
+(setf input-data (map 'list #'parse-line (test-input 2024 2)))
+
+(defvar sample-text "")
+(setf sample-text (aoc:split-lines "7 6 4 2 1
+1 2 7 8 9
+9 7 6 2 1
+1 3 2 4 5
+8 6 4 4 1
+1 3 6 7 9
+"))
+
+(defvar sample-data '())
+(setf sample-data (map 'list #'parse-line sample-text))
+
+(defun deltas (levels)
+  (map 'list #'-  (subseq levels 1) levels))
+
+(defun safe-levels (levels)
+  (let ((ds (deltas levels)))
+    (and
+     (or (every #'plusp ds) (every #'minusp ds))
+     (every (lambda (d) (>= 3 (abs d))) ds))))
+
+(defun remove-nth (n xs)
+  (append (subseq xs 0 (1- n)) (nthcdr n xs)))
+
+(defun safe-levels-with-dampener (levels)
+  (or (safe-levels levels)
+      (loop for n from 1 to (length levels)
+	    thereis	(safe-levels (remove-nth n levels)))))
+
+(defun part1 (data)
+  (loop for report in data
+	count (safe-levels report)))
+
+(defun part2 (data)
+  (loop for report in data
+	count (safe-levels-with-dampener report)))
+
+(defun solve-day ()
+  (format t "part1: ~A~%" (part1 input-data))
+  (format t "part2: ~A~%" (part2 input-data)))
diff --git a/tests/2024/day02-test.lisp b/tests/2024/day02-test.lisp
new file mode 100644
index 0000000..7e6137f
--- /dev/null
+++ b/tests/2024/day02-test.lisp
@@ -0,0 +1,41 @@
+(defpackage :aoc/2024/02/tests
+  (:use :cl :aoc :aoc/tests :aoc/2024/tests :parachute :aoc/2024/02))
+
+(in-package :aoc/2024/02/tests)
+
+(define-test suite-2024-02
+					;:parent suite-2024
+  )
+
+(define-test+run test-deltas
+  :parent suite-2024-02
+  (true (equalp '(1 1 1) (deltas '(1 2 3 4)))))
+
+(define-test+run test-safe-levels
+  :parent suite-2024-02
+  (true (safe-levels '(7 6 4 2 1)))  ; Safe because the levels are all decreasing by 1 or 2.
+  (false (safe-levels '(1 2 7 8 9))) ; Unsafe because 2 7 is an increase of 5.
+  (false (safe-levels '(9 7 6 2 1))) ; Unsafe because 6 2 is a decrease of 4.
+  (false (safe-levels '(1 3 2 4 5))) ; Unsafe because 1 3 is increasing but 3 2 is decreasing.
+  (false (safe-levels '(8 6 4 4 1))) ; Unsafe because 4 4 is neither an increase or a decrease.
+  (true (safe-levels '(1 3 6 7 9))) ; Safe because the levels are all increasing by 1, 2, or 3.
+  )
+
+(define-test+run test-safe-levels-with-dampener
+  :parent suite-2024-02
+  (true (safe-levels-with-dampener '(7 6 4 2 1)))  
+  (false (safe-levels-with-dampener '(1 2 7 8 9))) 
+  (false (safe-levels-with-dampener '(9 7 6 2 1))) 
+  (true (safe-levels-with-dampener '(1 3 2 4 5))) 
+  (true (safe-levels-with-dampener '(8 6 4 4 1))) 
+  (true (safe-levels-with-dampener '(1 3 6 7 9))) 
+  )
+(define-test+run test-part1
+  :parent suite-2024-02
+  (true (equalp 2 (part1 sample-data))))
+
+(define-test+run test-part2
+  :parent suite-2024-02
+  (true (equalp 31 (part2 sample-data))))
+
+